Pneumatic power tools are commonly employed in a variety of work places in order to accomplish various tasks. Typical pneumatic power tools include pneumatic fasteners, such as pneumatic nailers and pneumatic staplers. A typical system within a pnemutic fastener generates the desired hammering force by employing compressed air (typically supplied by a separate air compressor), a valve assembly including a valve plunger, and a piston assembly including a sliding piston that drives a long blade. In such system, the piston is forced downward when the air pressure above the piston head is greater than below it. Moreover, the piston is forced into an “up” position when the air pressure below the piston is greater than above it. In addition, a trigger assembly is employed to allow a user to control the actuation of the pneumatic fastener.
In use, the pneumatic fastener is actuated by a user activating the trigger assembly. Upon actuation, the trigger assembly closes the trigger valve while opening a passageway to the atmosphere as such compressed air is prevented from flowing above the valve plunger whereby pressure beneath the plunger is greater than pressure above the plunger. This configuration causes the valve plunger to rise up and compressed air to travel to the piston head. The piston and the blade are then driven downward by the compressed air causing a fastener (e.g. a nail or staple) to be propelled from the chamber. The downward sliding of the piston, in turn, channels the air inside the cylinder through a series of holes into a return air chamber. When a user then releases the trigger assembly, the plunger is pushed back into place by the compressed air and air flow to the piston head is blocked. In the absence of downward pressure, the piston head is also pushed back up by the compressed air in the return air chamber. As a result, the air above the piston head is forced out of the gun and into the atmosphere.
Although the standard pneumatic fastener, such as a nailer, works well for driving even thick nails through hard material such fasteners are disadvantageous in many respects. First, the standard pneumatic fastener typically employs functional features for controlling and directing air flow which involve expensive and time consuming manufacturing processes and result in decreased performance characteristics. For example, many pneumatic fasteners require a cross hole to be drilled and plugged through an outer cap or an angled hole to be drilled through such cap in order to get supply air from the air source, through the outer cap and to the back side of the valve piston chamber. One disadvantage associated with this design is possible significant increases in manufacturing costs, which in turn may be passed onto the consumer. An additional disadvantage associated with such configuration is that employment of machined holes provide rough surfaces (e.g. edges) over which the air must travel. The rough surfaces may increase air flow turbulence/friction thereby reducing the efficiency of air flow travel and possibly decreasing the efficiency of the pneumatic fastener. Current solutions to overcome increased friction typically involve the application of a lubricant to the rough surfaces. Utilization of such lubricants may increase the cost of operating pneumatic fasteners while also possibly simultaneously resulting in decreased productivity as the pneumatic fasteners must halt operation in order to have the lubricant provided. In addition, the aforementioned disadvantage is continuous for the lubricant has a limited useful lifespan and must be continuously replaced to assist in smoothing the surfaces over which the air must travel.
Therefore, it would be desirable to provide a pneumatic fastener which requires neither the machining of the outer cap to establish air flow patterns nor application of a lubricant to prevent increases in air flow friction.